Laser sintering (“LS”), also termed selective laser sintering, is a process whereby a dispenser deposits a layer of powdered material into a target area. A laser control mechanism, which typically includes a computer that houses the design of a desired article, modulates and moves a laser beam to selectively irradiate the powder layer within the defined boundaries of the design, resulting in melting of the powder on which the laser beam falls. The control mechanism operates the laser to selectively sinter sequential powder layers, eventually producing a completed article comprising a plurality of layers sintered together. A detailed description of LS technology can be found in U.S. Pat. Nos. 4,247,508, 4,863,538, 5,017,753, and 6,110,411, each incorporated herein by reference.
LS technology has enabled the direct manufacture of three-dimensional articles well suited to rapid prototyping and various other applications. Conventional powdered materials for use in LS have typically suffered from one or more drawbacks such as, for example, cost, ease of use in conventional LS machines, recyclability, and shrinkage problems when exposed to high process temperatures. Moreover, articles produced from conventional polymer powders via LS processes typically exhibit inferior mechanical properties relative to articles produced by more conventional manufacturing processes (e.g., injection molding). In addition, such articles are generally not suitable for use in elevated temperature environments due to degradation of mechanical properties.
Carbon fibers and glass fibers have been considered as filler materials to improve the mechanical properties of LS articles. Carbon fibers, however, are relatively expensive, may require careful handling to minimize or avoid particle inhalation issues (due to the particle size and bulk density typically associated with carbon fibers), can be difficult to process in LS equipment due to its black coloration and the additional infrared absorption associated therewith, and may not be suitable for producing white, light-colored and/or bright articles. As for glass fibers, they are relatively expensive and may be difficult to obtain in predictable commercial quantities of consistent and suitable quality.
Thus, there is a continuing need for improved powder compositions for use in producing LS articles that are cost effective, easy to use, and/or exhibit suitable mechanical properties at desired end use temperatures.